Some of the companies are quite old and have a complicated history of mergers and acquisitions. For example both AT&T and Verizon are descendants of Bell Teleph

Some of the companies are quite old and have a complicated history of mergers and acquisitions. For example both AT&T and Verizon are descendants of Bell Telephone Company, established in 1879. https://en.wikipedia.org/wiki/History_of_AT%26T https://en.wikipedia.org/wiki/History_of_AT%26T https://en.wikipedia.org/wiki/Verizon_Communications https://en.wikipedia.org/wiki/Verizon_Communications